Conventionally, when inspections and treatments are performed using an endoscope, air is insufflated into the lumen through an insufflation conduit provided in the endoscope to secure a field of view of the endoscope and secure an operational area of treatment tools. Air has been mainly used as the gas to be insufflated into the lumen in a conventional art, but carbon dioxide gas (CO2 gas) has been used in recent years. Since carbon dioxide gas has favorable bioabsorbability, there is little damage to the subject (patient). For this reason, there is a tendency for carbon dioxide gas to be used as a gas supply source.
The insufflation system which insufflates gas into the lumen has an advantage in that when carbon dioxide gas is manually insufflated into the lumen according to the operation of an operator, the operator can freely adjust an amount of gas to be insufflated into the lumen according to the intention of the operator, but has a disadvantage in that the operator needs to perform frequent operations in order to keep the pressure inside the lumen constant, thereby increasing an operational burden of the operator.
In view of this, there has been proposed an insufflation system having a function to automatically insufflate carbon dioxide gas into the lumen to make the pressure inside the lumen become a constant pressure (for example, see Japanese Patent Application Laid-Open No. 2009-131467 and No. 2012-231897). The insufflation systems can control the pressure inside the lumen to be stably maintained in a desired state without requiring the operator to perform complicated operations, and hence can reduce the operational burden of the operator.